1. Field of the Invention
The present invention relates to wireless communication and, more particularly, to an interworking technique between a mesh network and an external network.
2. Related Art
Recently, diverse wireless communication technologies are under development in line with the advancement of information communication technology. Among them, a wireless local area network (WLAN) is a technique allowing mobile terminals such as personal digital assistants (PDAs), laptop computers, portable multimedia players (PMPs), and the like, to wirelessly access the high speed Internet at homes or offices or in a particular service providing area based on a radio frequency technology.
Communications in the WLAN in conformity with the IEEE 802.11 are presupposed to be performed within an area called a basic service set (BSS). The BSS area may vary according to propagation characteristics of a wireless medium, so its boundary is somewhat indefinite. The BSS may be classified into an independent BSS (IBSS) and an infrastructure BSS. The former establishes a self-contained network, not allowing an access to a distribution system (DS), and the latter, which includes one or more access points (APs), a DS, and the like, generally refers to a BSS in which an AP is used for every communication process including communications between stations (STAs).
A station (STA) that intends to access a wireless network may search an accessible wireless network (BSS or IBSS), namely, a candidate AP, by using two methods as follows.
A first method is a passive scanning method using a beacon frame transmitted from an AP (or STA). Namely, an STA, which wants to access a wireless network, may receive beacon frames periodically transmitted from an AP that manages a pertinent BSS (or IBSS), and search an access BSS or IBSS.
A second method is an active scanning method. In this method, an STA, which wants to access a wireless network, first transmits a probe request frame. Then, an STA or an AP, which has received the probe request frame, responds by a probe response frame.
In the WLAN, a mesh network is defined as a special type of network. The mesh network may be a network supporting direct communications between a plurality of wireless devices having a relay function, without using an access point (AP). In terms of function, a distribution system (DS) of an AP may be substituted by interoperable wireless links or multi-hop paths between a plurality of APs. The mesh network allows one wireless device to establish a peer-to-peer wireless link with neighbor wireless devices and/or APs, having an advantage of enabling more flexible wireless connections.
In the mesh network, one wireless device may be connected to a plurality of wireless devices, establishing a plurality of communication paths. Such communication paths between the wireless devices are called wireless mesh links or simply mesh links or peer links. The wireless devices are called mesh points (MPs) but not meant to be limited thereto. Among the MPs, an MP that performs an AP function in addition to its relay function as described above is called a mesh access point (MAP).
The mesh network has advantages of flexibility in network establishment, reliability according to a detour path, and reduction in power consumption resulting from the reduction in a communication distance. In more detail the use of the mesh network enables MPs to establish a flexible network therebetween even in an area in which no communication network has been established.
In addition, in the mesh network, a plurality of detour paths can be secured as the plurality of MPs are connected to each other, so even if one MP has a trouble, data can be transmitted via another path. Also, although a communication coverage of one MP is not large, it can communicate by way of an adjacent MP, and thus, long distance (remote, wide area) communication can be performed even at a low power level.
However, the active scanning method employed by the STA that wants to access a wireless network cannot be applied as it is to a procedure for an MP to establish a new mesh network with another MP or access an established mesh network. The reason is because, a non-MP STA (when a station is simply mentioned, it refers to a non-AP STA without an MP function), an MP, a MAP, a non-MP AP (when an AP is simply mentioned, it refers to an AP without an MP function) may coexist in the mesh network, and in this situation the STA or the AP cannot become a candidate MP with which an MP can establish a mesh network.
In particular, the STA not supporting the wireless mesh network performs communication via the MAP, and in this case, those STAs not supporting the mesh network in conformity with IEEE 802.11s have connectivity only with the MAP. Thus, research on a method for transferring information about the STAs and the MAP having connectivity with the STAs to a mesh portal needs to be conducted to allow the STAs to interwork with an external network via the mesh portal.